Whats the wattage on your PSU?

Ok: thanks Frank. Only problem is I'll have to cross post so as to be able to respond to eyeofthehawks, I suppose. Also, I don't know whether or not this site operates the policy of deleting too many questions leading to a question ban, as at least one other SE site does, so I'd like to cross post for that reason too. @eyeofthehawks: I don't know and I'm not really eager to open up the PC to take a look at the moment. I don't have much time left before I was planning to go out plus I don't really fell up to opening the PC up right now. Thanks for your response though.

@eyeofthehawks To be honest I don't relish the thought of opening up the PC at all. Is there any other way to find this out? I have read on another post that forcing vsync in the Nvidia Control Panel helped with what seems could be a similar problem, so I plan to try that route first, God permitting.

Not that Im aware of George, unless theres a sticker on the case somewhere

@Alok Maybe this is true: I don't know whether the previous user, or even possibly someone prior to that, added the GTX 650 or whether that was the orginal card. The previous user was my father, but he may have aquired the PC from someone else.

@eyeofthehawks I opened up the PC yesterday and found that some of the info it gives on the PSU is 230V, Current 10A and Frequency 50-60Hz, so I guess that would make the wattage 230*10 = 2300W.

I have a hard time believing that. Your psu should say the wattage right on it

@eyeofthehawks Ok I've just taken another look at all the info which I wrote down on an envelope and at the bottom it says OUTPUT 500W, so I guess that would be it. I'm glad you said that: I appear to have misapplied the formula Electric Power = Current * Voltage

This wont be completely accurate, but its a nice estimator, fill it in as best you can support.asus.com/powersupply.aspx

@eyeofthehawks Ok many thanks. Just filled it in. I know everything is right unless there is an extra device or two, but I know I got the main stuff right: i.e. processor, VGA card, 2 USB devices and DVD. The Recommended Minimum Power Supply came back as 500W. An extra device or two does shift it up to 550W, so if there is an extra device or 2 I don't know about, it would be under the minimum. Do you think getting a voltage stabilizer could help and if so do you know if this or the purchase of a PSU with a higher wattage be a better first step?

@eyeofthehawks Also I notice that I've received conflicting advice, since ernie says that a PSU with greater wattage is liable to worsen the problem, rather than help, in his answer.

This should be taken out of gaming and into hardware now

It is already on Superuser. So I should just delete all the useful info on the gaming post?

By deleting the question?

Someone on there wants me to keep them updated: they're interested too.

Ok, so by moved to hardware, do you mean superuser.com?

I clicked delete, but got the message that it's not recommended that questions with answers be deleted as it can deprive users of knowledge or something similar and it can lead to a question ban, so I'll leave it.